000
FXUS63 KLSX 070336
AFDLSX

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE ST LOUIS MO
936 PM CST Fri Dec 6 2013

.UPDATE:
Issued at 923 PM CST Fri Dec 6 2013

The back edge of the mid cloud deck was clearing to the southeast
at around 25 kts and stretched from Fort Leonard Wood to St.
Louis to just south of Decatur. Based on this extrapolation it
should clear the entire CWA between 06-08z. Meanwhile the patch of
mid clouds across northeast Missouri into west central Illinois
continues to shrink with time. The clearing of the clouds combined
with the Arctic High continue to settle into the area will make
for an uncharacteristically cold night across the region, even for
early December, with lows 20-30 degrees below average. Locations
within the deeper snow pack across southeast Missouri into
southwest Illinois will be in the 0-5 degf range with wind chills
of 5 to 10 below.

Glass

&&

.SHORT TERM:  (Through Tonight)
Issued at 212 PM CST Fri Dec 6 2013

Plan to trim nrn edge of ongoing headlines where precip had ended
and will come to an end soon. Will determine which counties to
will be canceled closer to publish time.

Otherwise, focus will be temps and very cold wind chill values.

Ongoing sn is quickly pulling out of the area this afternoon.
Latest RADAR trends suggest, and mdls seem to agree, sn shud be
just E of the CWA by 00z. Have kept mention of flurries across ern
counties for a few hours this evening, but even flurries shud be
ending quickly with sunset. Clouds will also be quick to clear
out, but some mid clouds across wrn MO will move back into the
region as they break up this evening.

With clouds clearing out of the region, a nrly wind with persistent
CAA, and snowpack, temps shud plummet tonight. Have therefore
trended aob coolest MOS for tonight. Winds shud diminish somewhat,
but wind chill values will still be very close to advisory
criteria, which is -15 F. Have held off issuing an advisory
tonight, but one may be needed if winds do not diminish.

Tilly

.LONG TERM:  (Saturday through Next Friday)
Issued at 252 PM CST Fri Dec 6 2013

(Saturday through Monday)

Main focus will be the system impacting the region Sat night thru
Sun.

A brief mention for temps...have continued cold trend thru Sat for
obvious reasons.

For Sun, mdls lift the wrmfnt nwd thru the region late Sat night
and thru Sun as a s/w ejects out into the Plains. The
GFS/ECMWF/GEM are in rather good agreement with this fnt producing
some light precip as it lifts nwd. Have largely discounted the NAM
for this event for now. Latest guidance suggests this precip will
begin as sn. However, with the much warmer airmass lifting over
the snow field, granted it is only temps in the mid to upper 20s,
this shud present a FG problem as well as FZDZ. That said, there
are some locations that may switch back to SN due to a very cold
column that may reach the -10 C range to produce ice crystals
again. Uncertainty remains just how much ice accumulation this
system will generate. With sfc temps much colder than the current
system, only a trace of precip may have a huge impact on the area.
Latest mdl guidance suggests this precip will lift nwd thru the
region quicker than prev cycles and have adjusted POPs
accordingly.

(Tuesday through Friday)

Temps are expected to gradually moderate thru the period, but shud
finally reach above freezing late in the period as another system
approaches the area. Have kept POPs low given differences among
mdl guidance. However, what precip does fall is currently expected
to be rain. The forecast does mention FZRA as timing of onset will
determine type. Regardless, the rain will likely be falling onto a
very cold ground and may freeze even if air temps are above
freezing. This freezing will likely be short lived as temps
continue to warm.

Tilly

&&

.AVIATION:  (For the 00z TAFs through 00z Saturday Evening)
Issued at 524 PM CST Fri Dec 6 2013

VFR cloud deck will gradually clear the area tonight. Winds to
remain northerly due to a high pressure center located across the
northern Plains which is moving towards the Great Lakes.
Additional clouds will develop and spread across the terminals
late in the TAF period as the next disturbance approaches the
region.

Specifics for KSTL: VFR through the period.

Kanofsky

&&

.LSX WATCHES/WARNINGS/ADVISORIES:
MO...NONE.
IL...NONE.
&&

$$

WFO LSX